Non-ferrous continuous casting and rolling systems have been known for many years, and such systems for copper rod production are also well-known. These continuous rod production systems generally include apparatus for providing a continuous stream of molten metal to a casting machine in which the metal is solidified as a continuous cast bar, an in-line continuous rolling mill, an in-line rod cleaning apparatus, and a rod product coiling machine to collect the finished rod product for transport to further processing stations or for shipment.
The copper rod systems pioneered by The Southwire Company of Carrollton, Ga. USA initially produced copper rod at a production rate of about 10 tons per hour. The success of such systems is based on the economic advantages resulting from the continuous nature of the rod production and on the vastly improved copper rod product produced. Similar continuous systems are available for other non-ferrous products, such as aluminum and aluminum alloy rod, as well as for ferrous products. In the years since continuous copper rod was first achieved, the demand for further increased production economy based on greater throughput has driven the continuous casting technology to production rates of about 50 tons per hour or more. Because these manufacturing economies are available as a result of system improvements, production rate limitations of any of the system elements limits further economy of scale system improvements.
Coilers for coiling continuously produced metal rod and similar material have been developed for orbital coiling metal rod as it is initially and continuously discharged from a rolling mill or the like and for coiling the rod into a coil in which the loops are positioned so that the rod can be conveniently fed from the coil. The coil may also be packaged for transport for further processing. A well-known prior art orbital coiler is disclosed in U.S. Pat. No. 3,703,261, assigned to the assignee of the present invention.
The prior art orbital coiler produces epicyclic coils by the use of a turntable which rotates about a fixed axis of rotation and a flyer tube which rotates above the turntable about a substantially fixed axis of rotation that is displaced from the axis of rotation of the turntable. In the known prior art coiler, the flyer tube extends from an upper rod receiving end portion in the axis of rotation of the flyer tube above the coiling area and curves downwardly and outwardly to a lower rod discharge end portion having a constant radius. The discharge end moves in a circle about the axis of rotation of the flyer tube and is oriented so that metal rod passing into the receiving end exits the discharge end of the flyer tube and is formed into circular loops that drop to the rotating turntable.
In the prior art orbital coiler, the relationship between the diameter of the loops formed by the rotating flyer tube and the displacement of the axis of rotation of the flying tube relative to the axis of rotation of the turntable is such that each loop formed by the coiler includes within its circumference the axis of rotation of the turntable, which thus becomes the center line of the coil formed by the loops. The epicyclic displacement of successive loops relative to each other in a circular path around the turntable axis is a function of the rotational speed of the turntable and the linear speed of the metal rod as it passes through the flyer tube. The diameter of each loop may be varied by varying the angular speed of the discharge end of the flyer tube relative to the linear speed of the metal rod as it passes through the flyer tube. At a given operating speed, the constant radius portion of the flyer tube forms nearly perfect circular rod loops.
The prior art orbital coiler was originally designed to produce coils of large mass at a rate of approximately ten tons per hour and slightly more. As continuous casting and rolling of non-ferrous metals has increased from the lower production rate to substantially higher production rates, i.e., approximately fifty tons per hour and greater, it has been discovered that friction in the flyer tube portion of the coiler limits expansion of production capacity. For example, when producing 10 mm (3/8-inch) diameter copper rod at a rate of 60 tons per hour, rod entering the coiler is travelling in excess of 1800 meters per minute (6000 feet per minute), which is faster than the prior art flyer tube can readily accept without generating excess friction on the interior surfaces thereof. Friction, of course, increases with rod travel rate through the flyer tube and decreases with a decreasing flyer tube length.
Additionally, as the production rate increases, and particularly as the production rate increases above approximately forty tons per hour, the known flyer tube becomes subject to rapid wear and must be frequently replaced. The flyer tube is an expensive component part of the coiler, and its replacement necessitates interruption of the entire casting and rolling production process. It has also been discovered that simply reducing the length of the flyer tube to reduce excessive friction results in non circular or out-of-round loops which do not form into acceptable coils.
One function of the prior art flyer tube was to form the rod into circular loops. The lower discharge portion of the flyer tube was designed with a constant radius section such that metal rod to be coiled was fed into the receiving end of the flyer tube and was discharged from the discharge end of the flyer tube in the form of a continuous series of nearly perfect circular loops. The loops were simply permitted to drop to the surface of the turntable. The elongated, constant radius portion of the flyer tube functioned to limit the loop diameter and to maximize perfect circularity of the rod loops formed at a given production rate.
Shortening the flyer tube to reduce internal friction resulted in imperfect circular loops because the rod loop diameter was not well controlled. The imperfectly formed circular loops resulted in non-uniform coils of rod which are undesirable. This is true especially at the high loop forming speeds resulting from the higher production rates. Thus, while shortening the flyer tube does reduce friction in the flyer tube, it does not permit operation of the coiler at higher production rates because the coils formed at such higher production rates are unsatisfactory.